Ketamine, a dissociative anesthetic, is being used in the treatment of Complex Regional Pain Syndrome with anecdotal success. During the infusion the patient is monitored constantly, and it should be administered only by a qualified physician such as an anesthesiologist. The theory of ketamine use in CRPS is primarily advanced by neurologist Dr. Robert J. Schwartzman of Drexel University College of Medicine in Philadelphia and researchers at the University of Tübingen in Germany but was first introduced in the United States by Doctor Ronald Harbut of Little Rock, Arkansas. The hypothesis is that ketamine blocks NMDA receptors that might reboot aberrant brain activity.
There are two treatment modalities; the first consists of a low-dose subanesethesia Ketamine infusion of 10–90 mg per hour over several treatment days. This can be delivered on an outpatient basis and is called the awake or subanesethesia technique.
One study demonstrated that 83% of the patients who participated had complete relief, and many others had some relief of the symptoms. Another evaluation of a ten-day infusion of intravenous ketamine (awake technique) in the CRPS patient concluded that "a four-hour ketamine infusion escalated from 40–80 mg over a 10-day period can result in a significant reduction of pain with increased mobility and a tendency to decreased autonomic dysregulation". Unfortunately, these study designs are very prone to bias, which means high quality randomised controlled trials of ketamine infusion for CRPS are still needed to learn about its effects and side effects.
The second treatment modality consists of putting the patient into a medically induced coma, then administering an extremely high dosage of ketamine; typically between 600 and 900 mg. This version, currently not allowed in the United States, was also banned in Germany before 2010. The only trials are taking place now only in Monterrey, Nuevo León, Mexico.